net/rds/ib_send.c

   1 /*
   2  * Copyright (c) 2006 Oracle.  All rights reserved.
   3  *
   4  * This software is available to you under a choice of one of two
   5  * licenses.  You may choose to be licensed under the terms of the GNU
   6  * General Public License (GPL) Version 2, available from the file
   7  * COPYING in the main directory of this source tree, or the
   8  * OpenIB.org BSD license below:
   9  *
  10  *     Redistribution and use in source and binary forms, with or
  11  *     without modification, are permitted provided that the following
  12  *     conditions are met:
  13  *
  14  *      - Redistributions of source code must retain the above
  15  *        copyright notice, this list of conditions and the following
  16  *        disclaimer.
  17  *
  18  *      - Redistributions in binary form must reproduce the above
  19  *        copyright notice, this list of conditions and the following
  20  *        disclaimer in the documentation and/or other materials
  21  *        provided with the distribution.
  22  *
  23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  27  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  28  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  29  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  30  * SOFTWARE.
  31  *
  32  */
  33 #include <linux/kernel.h>
  34 #include <linux/in.h>
  35 #include <linux/device.h>
  36 #include <linux/dmapool.h>
  37
  38 #include "rds.h"
  39 #include "rdma.h"
  40 #include "ib.h"
  41
  42 static void rds_ib_send_rdma_complete(struct rds_message *rm,
  43                                       int wc_status)
  44 {
  45         int notify_status;
  46
  47         switch (wc_status) {
  48         case IB_WC_WR_FLUSH_ERR:
  49                 return;
  50
  51         case IB_WC_SUCCESS:
  52                 notify_status = RDS_RDMA_SUCCESS;
  53                 break;
  54
  55         case IB_WC_REM_ACCESS_ERR:
  56                 notify_status = RDS_RDMA_REMOTE_ERROR;
  57                 break;
  58
  59         default:
  60                 notify_status = RDS_RDMA_OTHER_ERROR;
  61                 break;
  62         }
  63         rds_rdma_send_complete(rm, notify_status);
  64 }
  65
  66 static void rds_ib_send_unmap_rdma(struct rds_ib_connection *ic,
  67                                    struct rds_rdma_op *op)
  68 {
  69         if (op->r_mapped) {
  70                 ib_dma_unmap_sg(ic->i_cm_id->device,
  71                         op->r_sg, op->r_nents,
  72                         op->r_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
  73                 op->r_mapped = 0;
  74         }
  75 }
  76
  77 static void rds_ib_send_unmap_rm(struct rds_ib_connection *ic,
  78                           struct rds_ib_send_work *send,
  79                           int wc_status)
  80 {
  81         struct rds_message *rm = send->s_rm;
  82
  83         rdsdebug("ic %p send %p rm %p\n", ic, send, rm);
  84
  85         ib_dma_unmap_sg(ic->i_cm_id->device,
  86                      rm->m_sg, rm->m_nents,
  87                      DMA_TO_DEVICE);
  88
  89         if (rm->m_rdma_op != NULL) {
  90                 rds_ib_send_unmap_rdma(ic, rm->m_rdma_op);
  91
  92                 /* If the user asked for a completion notification on this
  93                  * message, we can implement three different semantics:
  94                  *  1.  Notify when we received the ACK on the RDS message
  95                  *      that was queued with the RDMA. This provides reliable
  96                  *      notification of RDMA status at the expense of a one-way
  97                  *      packet delay.
  98                  *  2.  Notify when the IB stack gives us the completion event for
  99                  *      the RDMA operation.
 100                  *  3.  Notify when the IB stack gives us the completion event for
 101                  *      the accompanying RDS messages.
 102                  * Here, we implement approach #3. To implement approach #2,
 103                  * call rds_rdma_send_complete from the cq_handler. To implement #1,
 104                  * don't call rds_rdma_send_complete at all, and fall back to the notify
 105                  * handling in the ACK processing code.
 106                  *
 107                  * Note: There's no need to explicitly sync any RDMA buffers using
 108                  * ib_dma_sync_sg_for_cpu - the completion for the RDMA
 109                  * operation itself unmapped the RDMA buffers, which takes care
 110                  * of synching.
 111                  */
 112                 rds_ib_send_rdma_complete(rm, wc_status);
 113
 114                 if (rm->m_rdma_op->r_write)
 115                         rds_stats_add(s_send_rdma_bytes, rm->m_rdma_op->r_bytes);
 116                 else
 117                         rds_stats_add(s_recv_rdma_bytes, rm->m_rdma_op->r_bytes);
 118         }
 119
 120         /* If anyone waited for this message to get flushed out, wake
 121          * them up now */
 122         rds_message_unmapped(rm);
 123
 124         rds_message_put(rm);
 125         send->s_rm = NULL;
 126 }
 127
 128 void rds_ib_send_init_ring(struct rds_ib_connection *ic)
 129 {
 130         struct rds_ib_send_work *send;
 131         u32 i;
 132
 133         for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
 134                 struct ib_sge *sge;
 135
 136                 send->s_rm = NULL;
 137                 send->s_op = NULL;
 138
 139                 send->s_wr.wr_id = i;
 140                 send->s_wr.sg_list = send->s_sge;
 141                 send->s_wr.num_sge = 1;
 142                 send->s_wr.opcode = IB_WR_SEND;
 143                 send->s_wr.send_flags = 0;
 144                 send->s_wr.ex.imm_data = 0;
 145
 146                 sge = rds_ib_data_sge(ic, send->s_sge);
 147                 sge->lkey = ic->i_mr->lkey;
 148
 149                 sge = rds_ib_header_sge(ic, send->s_sge);
 150                 sge->addr = ic->i_send_hdrs_dma + (i * sizeof(struct rds_header));
 151                 sge->length = sizeof(struct rds_header);
 152                 sge->lkey = ic->i_mr->lkey;
 153         }
 154 }
 155
 156 void rds_ib_send_clear_ring(struct rds_ib_connection *ic)
 157 {
 158         struct rds_ib_send_work *send;
 159         u32 i;
 160
 161         for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
 162                 if (send->s_wr.opcode == 0xdead)
 163                         continue;
 164                 if (send->s_rm)
 165                         rds_ib_send_unmap_rm(ic, send, IB_WC_WR_FLUSH_ERR);
 166                 if (send->s_op)
 167                         rds_ib_send_unmap_rdma(ic, send->s_op);
 168         }
 169 }
 170
 171 /*
 172  * The _oldest/_free ring operations here race cleanly with the alloc/unalloc
 173  * operations performed in the send path.  As the sender allocs and potentially
 174  * unallocs the next free entry in the ring it doesn't alter which is
 175  * the next to be freed, which is what this is concerned with.
 176  */
 177 void rds_ib_send_cq_comp_handler(struct ib_cq *cq, void *context)
 178 {
 179         struct rds_connection *conn = context;
 180         struct rds_ib_connection *ic = conn->c_transport_data;
 181         struct ib_wc wc;
 182         struct rds_ib_send_work *send;
 183         u32 completed;
 184         u32 oldest;
 185         u32 i = 0;
 186         int ret;
 187
 188         rdsdebug("cq %p conn %p\n", cq, conn);
 189         rds_ib_stats_inc(s_ib_tx_cq_call);
 190         ret = ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
 191         if (ret)
 192                 rdsdebug("ib_req_notify_cq send failed: %d\n", ret);
 193
 194         while (ib_poll_cq(cq, 1, &wc) > 0) {
 195                 rdsdebug("wc wr_id 0x%llx status %u byte_len %u imm_data %u\n",
 196                          (unsigned long long)wc.wr_id, wc.status, wc.byte_len,
 197                          be32_to_cpu(wc.ex.imm_data));
 198                 rds_ib_stats_inc(s_ib_tx_cq_event);
 199
 200                 if (wc.wr_id == RDS_IB_ACK_WR_ID) {
 201                         if (ic->i_ack_queued + HZ/2 < jiffies)
 202                                 rds_ib_stats_inc(s_ib_tx_stalled);
 203                         rds_ib_ack_send_complete(ic);
 204                         continue;
 205                 }
 206
 207                 oldest = rds_ib_ring_oldest(&ic->i_send_ring);
 208
 209                 completed = rds_ib_ring_completed(&ic->i_send_ring, wc.wr_id, oldest);
 210
 211                 for (i = 0; i < completed; i++) {
 212                         send = &ic->i_sends[oldest];
 213
 214                         /* In the error case, wc.opcode sometimes contains garbage */
 215                         switch (send->s_wr.opcode) {
 216                         case IB_WR_SEND:
 217                                 if (send->s_rm)
 218                                         rds_ib_send_unmap_rm(ic, send, wc.status);
 219                                 break;
 220                         case IB_WR_RDMA_WRITE:
 221                         case IB_WR_RDMA_READ:
 222                                 /* Nothing to be done - the SG list will be unmapped
 223                                  * when the SEND completes. */
 224                                 break;
 225                         default:
 226                                 if (printk_ratelimit())
 227                                         printk(KERN_NOTICE
 228                                                 "RDS/IB: %s: unexpected opcode 0x%x in WR!\n",
 229                                                 __func__, send->s_wr.opcode);
 230                                 break;
 231                         }
 232
 233                         send->s_wr.opcode = 0xdead;
 234                         send->s_wr.num_sge = 1;
 235                         if (send->s_queued + HZ/2 < jiffies)
 236                                 rds_ib_stats_inc(s_ib_tx_stalled);
 237
 238                         /* If a RDMA operation produced an error, signal this right
 239                          * away. If we don't, the subsequent SEND that goes with this
 240                          * RDMA will be canceled with ERR_WFLUSH, and the application
 241                          * never learn that the RDMA failed. */
 242                         if (unlikely(wc.status == IB_WC_REM_ACCESS_ERR && send->s_op)) {
 243                                 struct rds_message *rm;
 244
 245                                 rm = rds_send_get_message(conn, send->s_op);
 246                                 if (rm)
 247                                         rds_ib_send_rdma_complete(rm, wc.status);
 248                         }
 249
 250                         oldest = (oldest + 1) % ic->i_send_ring.w_nr;
 251                 }
 252
 253                 rds_ib_ring_free(&ic->i_send_ring, completed);
 254
 255                 if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags) ||
 256                     test_bit(0, &conn->c_map_queued))
 257                         queue_delayed_work(rds_wq, &conn->c_send_w, 0);
 258
 259                 /* We expect errors as the qp is drained during shutdown */
 260                 if (wc.status != IB_WC_SUCCESS && rds_conn_up(conn)) {
 261                         rds_ib_conn_error(conn,
 262                                 "send completion on %pI4 "
 263                                 "had status %u, disconnecting and reconnecting\n",
 264                                 &conn->c_faddr, wc.status);
 265                 }
 266         }
 267 }
 268
 269 /*
 270  * This is the main function for allocating credits when sending
 271  * messages.
 272  *
 273  * Conceptually, we have two counters:
 274  *  -   send credits: this tells us how many WRs we're allowed
 275  *      to submit without overruning the reciever's queue. For
 276  *      each SEND WR we post, we decrement this by one.
 277  *
 278  *  -   posted credits: this tells us how many WRs we recently
 279  *      posted to the receive queue. This value is transferred
 280  *      to the peer as a "credit update" in a RDS header field.
 281  *      Every time we transmit credits to the peer, we subtract
 282  *      the amount of transferred credits from this counter.
 283  *
 284  * It is essential that we avoid situations where both sides have
 285  * exhausted their send credits, and are unable to send new credits
 286  * to the peer. We achieve this by requiring that we send at least
 287  * one credit update to the peer before exhausting our credits.
 288  * When new credits arrive, we subtract one credit that is withheld
 289  * until we've posted new buffers and are ready to transmit these
 290  * credits (see rds_ib_send_add_credits below).
 291  *
 292  * The RDS send code is essentially single-threaded; rds_send_xmit
 293  * grabs c_send_lock to ensure exclusive access to the send ring.
 294  * However, the ACK sending code is independent and can race with
 295  * message SENDs.
 296  *
 297  * In the send path, we need to update the counters for send credits
 298  * and the counter of posted buffers atomically - when we use the
 299  * last available credit, we cannot allow another thread to race us
 300  * and grab the posted credits counter.  Hence, we have to use a
 301  * spinlock to protect the credit counter, or use atomics.
 302  *
 303  * Spinlocks shared between the send and the receive path are bad,
 304  * because they create unnecessary delays. An early implementation
 305  * using a spinlock showed a 5% degradation in throughput at some
 306  * loads.
 307  *
 308  * This implementation avoids spinlocks completely, putting both
 309  * counters into a single atomic, and updating that atomic using
 310  * atomic_add (in the receive path, when receiving fresh credits),
 311  * and using atomic_cmpxchg when updating the two counters.
 312  */
 313 int rds_ib_send_grab_credits(struct rds_ib_connection *ic,
 314                              u32 wanted, u32 *adv_credits, int need_posted, int max_posted)
 315 {
 316         unsigned int avail, posted, got = 0, advertise;
 317         long oldval, newval;
 318
 319         *adv_credits = 0;
 320         if (!ic->i_flowctl)
 321                 return wanted;
 322
 323 try_again:
 324         advertise = 0;
 325         oldval = newval = atomic_read(&ic->i_credits);
 326         posted = IB_GET_POST_CREDITS(oldval);
 327         avail = IB_GET_SEND_CREDITS(oldval);
 328
 329         rdsdebug("rds_ib_send_grab_credits(%u): credits=%u posted=%u\n",
 330                         wanted, avail, posted);
 331
 332         /* The last credit must be used to send a credit update. */
 333         if (avail && !posted)
 334                 avail--;
 335
 336         if (avail < wanted) {
 337                 struct rds_connection *conn = ic->i_cm_id->context;
 338
 339                 /* Oops, there aren't that many credits left! */
 340                 set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
 341                 got = avail;
 342         } else {
 343                 /* Sometimes you get what you want, lalala. */
 344                 got = wanted;
 345         }
 346         newval -= IB_SET_SEND_CREDITS(got);
 347
 348         /*
 349          * If need_posted is non-zero, then the caller wants
 350          * the posted regardless of whether any send credits are
 351          * available.
 352          */
 353         if (posted && (got || need_posted)) {
 354                 advertise = min_t(unsigned int, posted, max_posted);
 355                 newval -= IB_SET_POST_CREDITS(advertise);
 356         }
 357
 358         /* Finally bill everything */
 359         if (atomic_cmpxchg(&ic->i_credits, oldval, newval) != oldval)
 360                 goto try_again;
 361
 362         *adv_credits = advertise;
 363         return got;
 364 }
 365
 366 void rds_ib_send_add_credits(struct rds_connection *conn, unsigned int credits)
 367 {
 368         struct rds_ib_connection *ic = conn->c_transport_data;
 369
 370         if (credits == 0)
 371                 return;
 372
 373         rdsdebug("rds_ib_send_add_credits(%u): current=%u%s\n",
 374                         credits,
 375                         IB_GET_SEND_CREDITS(atomic_read(&ic->i_credits)),
 376                         test_bit(RDS_LL_SEND_FULL, &conn->c_flags) ? ", ll_send_full" : "");
 377
 378         atomic_add(IB_SET_SEND_CREDITS(credits), &ic->i_credits);
 379         if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags))
 380                 queue_delayed_work(rds_wq, &conn->c_send_w, 0);
 381
 382         WARN_ON(IB_GET_SEND_CREDITS(credits) >= 16384);
 383
 384         rds_ib_stats_inc(s_ib_rx_credit_updates);
 385 }
 386
 387 void rds_ib_advertise_credits(struct rds_connection *conn, unsigned int posted)
 388 {
 389         struct rds_ib_connection *ic = conn->c_transport_data;
 390
 391         if (posted == 0)
 392                 return;
 393
 394         atomic_add(IB_SET_POST_CREDITS(posted), &ic->i_credits);
 395
 396         /* Decide whether to send an update to the peer now.
 397          * If we would send a credit update for every single buffer we
 398          * post, we would end up with an ACK storm (ACK arrives,
 399          * consumes buffer, we refill the ring, send ACK to remote
 400          * advertising the newly posted buffer... ad inf)
 401          *
 402          * Performance pretty much depends on how often we send
 403          * credit updates - too frequent updates mean lots of ACKs.
 404          * Too infrequent updates, and the peer will run out of
 405          * credits and has to throttle.
 406          * For the time being, 16 seems to be a good compromise.
 407          */
 408         if (IB_GET_POST_CREDITS(atomic_read(&ic->i_credits)) >= 16)
 409                 set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
 410 }
 411
 412 static inline void
 413 rds_ib_xmit_populate_wr(struct rds_ib_connection *ic,
 414                 struct rds_ib_send_work *send, unsigned int pos,
 415                 unsigned long buffer, unsigned int length,
 416                 int send_flags)
 417 {
 418         struct ib_sge *sge;
 419
 420         WARN_ON(pos != send - ic->i_sends);
 421
 422         send->s_wr.send_flags = send_flags;
 423         send->s_wr.opcode = IB_WR_SEND;
 424         send->s_wr.num_sge = 2;
 425         send->s_wr.next = NULL;
 426         send->s_queued = jiffies;
 427         send->s_op = NULL;
 428
 429         if (length != 0) {
 430                 sge = rds_ib_data_sge(ic, send->s_sge);
 431                 sge->addr = buffer;
 432                 sge->length = length;
 433                 sge->lkey = ic->i_mr->lkey;
 434
 435                 sge = rds_ib_header_sge(ic, send->s_sge);
 436         } else {
 437                 /* We're sending a packet with no payload. There is only
 438                  * one SGE */
 439                 send->s_wr.num_sge = 1;
 440                 sge = &send->s_sge[0];
 441         }
 442
 443         sge->addr = ic->i_send_hdrs_dma + (pos * sizeof(struct rds_header));
 444         sge->length = sizeof(struct rds_header);
 445         sge->lkey = ic->i_mr->lkey;
 446 }
 447
 448 /*
 449  * This can be called multiple times for a given message.  The first time
 450  * we see a message we map its scatterlist into the IB device so that
 451  * we can provide that mapped address to the IB scatter gather entries
 452  * in the IB work requests.  We translate the scatterlist into a series
 453  * of work requests that fragment the message.  These work requests complete
 454  * in order so we pass ownership of the message to the completion handler
 455  * once we send the final fragment.
 456  *
 457  * The RDS core uses the c_send_lock to only enter this function once
 458  * per connection.  This makes sure that the tx ring alloc/unalloc pairs
 459  * don't get out of sync and confuse the ring.
 460  */
 461 int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 462                 unsigned int hdr_off, unsigned int sg, unsigned int off)
 463 {
 464         struct rds_ib_connection *ic = conn->c_transport_data;
 465         struct ib_device *dev = ic->i_cm_id->device;
 466         struct rds_ib_send_work *send = NULL;
 467         struct rds_ib_send_work *first;
 468         struct rds_ib_send_work *prev;
 469         struct ib_send_wr *failed_wr;
 470         struct scatterlist *scat;
 471         u32 pos;
 472         u32 i;
 473         u32 work_alloc;
 474         u32 credit_alloc;
 475         u32 posted;
 476         u32 adv_credits = 0;
 477         int send_flags = 0;
 478         int sent;
 479         int ret;
 480         int flow_controlled = 0;
 481
 482         BUG_ON(off % RDS_FRAG_SIZE);
 483         BUG_ON(hdr_off != 0 && hdr_off != sizeof(struct rds_header));
 484
 485         /* FIXME we may overallocate here */
 486         if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0)
 487                 i = 1;
 488         else
 489                 i = ceil(be32_to_cpu(rm->m_inc.i_hdr.h_len), RDS_FRAG_SIZE);
 490
 491         work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
 492         if (work_alloc == 0) {
 493                 set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
 494                 rds_ib_stats_inc(s_ib_tx_ring_full);
 495                 ret = -ENOMEM;
 496                 goto out;
 497         }
 498
 499         credit_alloc = work_alloc;
 500         if (ic->i_flowctl) {
 501                 credit_alloc = rds_ib_send_grab_credits(ic, work_alloc, &posted, 0, RDS_MAX_ADV_CREDIT);
 502                 adv_credits += posted;
 503                 if (credit_alloc < work_alloc) {
 504                         rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - credit_alloc);
 505                         work_alloc = credit_alloc;
 506                         flow_controlled++;
 507                 }
 508                 if (work_alloc == 0) {
 509                         set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
 510                         rds_ib_stats_inc(s_ib_tx_throttle);
 511                         ret = -ENOMEM;
 512                         goto out;
 513                 }
 514         }
 515
 516         /* map the message the first time we see it */
 517         if (ic->i_rm == NULL) {
 518                 /*
 519                 printk(KERN_NOTICE "rds_ib_xmit prep msg dport=%u flags=0x%x len=%d\n",
 520                                 be16_to_cpu(rm->m_inc.i_hdr.h_dport),
 521                                 rm->m_inc.i_hdr.h_flags,
 522                                 be32_to_cpu(rm->m_inc.i_hdr.h_len));
 523                    */
 524                 if (rm->m_nents) {
 525                         rm->m_count = ib_dma_map_sg(dev,
 526                                          rm->m_sg, rm->m_nents, DMA_TO_DEVICE);
 527                         rdsdebug("ic %p mapping rm %p: %d\n", ic, rm, rm->m_count);
 528                         if (rm->m_count == 0) {
 529                                 rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
 530                                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
 531                                 ret = -ENOMEM; /* XXX ? */
 532                                 goto out;
 533                         }
 534                 } else {
 535                         rm->m_count = 0;
 536                 }
 537
 538                 ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
 539                 ic->i_unsignaled_bytes = rds_ib_sysctl_max_unsig_bytes;
 540                 rds_message_addref(rm);
 541                 ic->i_rm = rm;
 542
 543                 /* Finalize the header */
 544                 if (test_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags))
 545                         rm->m_inc.i_hdr.h_flags |= RDS_FLAG_ACK_REQUIRED;
 546                 if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
 547                         rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;
 548
 549                 /* If it has a RDMA op, tell the peer we did it. This is
 550                  * used by the peer to release use-once RDMA MRs. */
 551                 if (rm->m_rdma_op) {
 552                         struct rds_ext_header_rdma ext_hdr;
 553
 554                         ext_hdr.h_rdma_rkey = cpu_to_be32(rm->m_rdma_op->r_key);
 555                         rds_message_add_extension(&rm->m_inc.i_hdr,
 556                                         RDS_EXTHDR_RDMA, &ext_hdr, sizeof(ext_hdr));
 557                 }
 558                 if (rm->m_rdma_cookie) {
 559                         rds_message_add_rdma_dest_extension(&rm->m_inc.i_hdr,
 560                                         rds_rdma_cookie_key(rm->m_rdma_cookie),
 561                                         rds_rdma_cookie_offset(rm->m_rdma_cookie));
 562                 }
 563
 564                 /* Note - rds_ib_piggyb_ack clears the ACK_REQUIRED bit, so
 565                  * we should not do this unless we have a chance of at least
 566                  * sticking the header into the send ring. Which is why we
 567                  * should call rds_ib_ring_alloc first. */
 568                 rm->m_inc.i_hdr.h_ack = cpu_to_be64(rds_ib_piggyb_ack(ic));
 569                 rds_message_make_checksum(&rm->m_inc.i_hdr);
 570
 571                 /*
 572                  * Update adv_credits since we reset the ACK_REQUIRED bit.
 573                  */
 574                 rds_ib_send_grab_credits(ic, 0, &posted, 1, RDS_MAX_ADV_CREDIT - adv_credits);
 575                 adv_credits += posted;
 576                 BUG_ON(adv_credits > 255);
 577         }
 578
 579         send = &ic->i_sends[pos];
 580         first = send;
 581         prev = NULL;
 582         scat = &rm->m_sg[sg];
 583         sent = 0;
 584         i = 0;
 585
 586         /* Sometimes you want to put a fence between an RDMA
 587          * READ and the following SEND.
 588          * We could either do this all the time
 589          * or when requested by the user. Right now, we let
 590          * the application choose.
 591          */
 592         if (rm->m_rdma_op && rm->m_rdma_op->r_fence)
 593                 send_flags = IB_SEND_FENCE;
 594
 595         /*
 596          * We could be copying the header into the unused tail of the page.
 597          * That would need to be changed in the future when those pages might
 598          * be mapped userspace pages or page cache pages.  So instead we always
 599          * use a second sge and our long-lived ring of mapped headers.  We send
 600          * the header after the data so that the data payload can be aligned on
 601          * the receiver.
 602          */
 603
 604         /* handle a 0-len message */
 605         if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0) {
 606                 rds_ib_xmit_populate_wr(ic, send, pos, 0, 0, send_flags);
 607                 goto add_header;
 608         }
 609
 610         /* if there's data reference it with a chain of work reqs */
 611         for (; i < work_alloc && scat != &rm->m_sg[rm->m_count]; i++) {
 612                 unsigned int len;
 613
 614                 send = &ic->i_sends[pos];
 615
 616                 len = min(RDS_FRAG_SIZE, ib_sg_dma_len(dev, scat) - off);
 617                 rds_ib_xmit_populate_wr(ic, send, pos,
 618                                 ib_sg_dma_address(dev, scat) + off, len,
 619                                 send_flags);
 620
 621                 /*
 622                  * We want to delay signaling completions just enough to get
 623                  * the batching benefits but not so much that we create dead time
 624                  * on the wire.
 625                  */
 626                 if (ic->i_unsignaled_wrs-- == 0) {
 627                         ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
 628                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 629                 }
 630
 631                 ic->i_unsignaled_bytes -= len;
 632                 if (ic->i_unsignaled_bytes <= 0) {
 633                         ic->i_unsignaled_bytes = rds_ib_sysctl_max_unsig_bytes;
 634                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 635                 }
 636
 637                 /*
 638                  * Always signal the last one if we're stopping due to flow control.
 639                  */
 640                 if (flow_controlled && i == (work_alloc-1))
 641                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 642
 643                 rdsdebug("send %p wr %p num_sge %u next %p\n", send,
 644                          &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
 645
 646                 sent += len;
 647                 off += len;
 648                 if (off == ib_sg_dma_len(dev, scat)) {
 649                         scat++;
 650                         off = 0;
 651                 }
 652
 653 add_header:
 654                 /* Tack on the header after the data. The header SGE should already
 655                  * have been set up to point to the right header buffer. */
 656                 memcpy(&ic->i_send_hdrs[pos], &rm->m_inc.i_hdr, sizeof(struct rds_header));
 657
 658                 if (0) {
 659                         struct rds_header *hdr = &ic->i_send_hdrs[pos];
 660
 661                         printk(KERN_NOTICE "send WR dport=%u flags=0x%x len=%d\n",
 662                                 be16_to_cpu(hdr->h_dport),
 663                                 hdr->h_flags,
 664                                 be32_to_cpu(hdr->h_len));
 665                 }
 666                 if (adv_credits) {
 667                         struct rds_header *hdr = &ic->i_send_hdrs[pos];
 668
 669                         /* add credit and redo the header checksum */
 670                         hdr->h_credit = adv_credits;
 671                         rds_message_make_checksum(hdr);
 672                         adv_credits = 0;
 673                         rds_ib_stats_inc(s_ib_tx_credit_updates);
 674                 }
 675
 676                 if (prev)
 677                         prev->s_wr.next = &send->s_wr;
 678                 prev = send;
 679
 680                 pos = (pos + 1) % ic->i_send_ring.w_nr;
 681         }
 682
 683         /* Account the RDS header in the number of bytes we sent, but just once.
 684          * The caller has no concept of fragmentation. */
 685         if (hdr_off == 0)
 686                 sent += sizeof(struct rds_header);
 687
 688         /* if we finished the message then send completion owns it */
 689         if (scat == &rm->m_sg[rm->m_count]) {
 690                 prev->s_rm = ic->i_rm;
 691                 prev->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 692                 ic->i_rm = NULL;
 693         }
 694
 695         if (i < work_alloc) {
 696                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
 697                 work_alloc = i;
 698         }
 699         if (ic->i_flowctl && i < credit_alloc)
 700                 rds_ib_send_add_credits(conn, credit_alloc - i);
 701
 702         /* XXX need to worry about failed_wr and partial sends. */
 703         failed_wr = &first->s_wr;
 704         ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
 705         rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
 706                  first, &first->s_wr, ret, failed_wr);
 707         BUG_ON(failed_wr != &first->s_wr);
 708         if (ret) {
 709                 printk(KERN_WARNING "RDS/IB: ib_post_send to %pI4 "
 710                        "returned %d\n", &conn->c_faddr, ret);
 711                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
 712                 if (prev->s_rm) {
 713                         ic->i_rm = prev->s_rm;
 714                         prev->s_rm = NULL;
 715                 }
 716
 717                 rds_ib_conn_error(ic->conn, "ib_post_send failed\n");
 718                 goto out;
 719         }
 720
 721         ret = sent;
 722 out:
 723         BUG_ON(adv_credits);
 724         return ret;
 725 }
 726
 727 int rds_ib_xmit_rdma(struct rds_connection *conn, struct rds_rdma_op *op)
 728 {
 729         struct rds_ib_connection *ic = conn->c_transport_data;
 730         struct rds_ib_send_work *send = NULL;
 731         struct rds_ib_send_work *first;
 732         struct rds_ib_send_work *prev;
 733         struct ib_send_wr *failed_wr;
 734         struct rds_ib_device *rds_ibdev;
 735         struct scatterlist *scat;
 736         unsigned long len;
 737         u64 remote_addr = op->r_remote_addr;
 738         u32 pos;
 739         u32 work_alloc;
 740         u32 i;
 741         u32 j;
 742         int sent;
 743         int ret;
 744         int num_sge;
 745
 746         rds_ibdev = ib_get_client_data(ic->i_cm_id->device, &rds_ib_client);
 747
 748         /* map the message the first time we see it */
 749         if (!op->r_mapped) {
 750                 op->r_count = ib_dma_map_sg(ic->i_cm_id->device,
 751                                         op->r_sg, op->r_nents, (op->r_write) ?
 752                                         DMA_TO_DEVICE : DMA_FROM_DEVICE);
 753                 rdsdebug("ic %p mapping op %p: %d\n", ic, op, op->r_count);
 754                 if (op->r_count == 0) {
 755                         rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
 756                         ret = -ENOMEM; /* XXX ? */
 757                         goto out;
 758                 }
 759
 760                 op->r_mapped = 1;
 761         }
 762
 763         /*
 764          * Instead of knowing how to return a partial rdma read/write we insist that there
 765          * be enough work requests to send the entire message.
 766          */
 767         i = ceil(op->r_count, rds_ibdev->max_sge);
 768
 769         work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
 770         if (work_alloc != i) {
 771                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
 772                 rds_ib_stats_inc(s_ib_tx_ring_full);
 773                 ret = -ENOMEM;
 774                 goto out;
 775         }
 776
 777         send = &ic->i_sends[pos];
 778         first = send;
 779         prev = NULL;
 780         scat = &op->r_sg[0];
 781         sent = 0;
 782         num_sge = op->r_count;
 783
 784         for (i = 0; i < work_alloc && scat != &op->r_sg[op->r_count]; i++) {
 785                 send->s_wr.send_flags = 0;
 786                 send->s_queued = jiffies;
 787                 /*
 788                  * We want to delay signaling completions just enough to get
 789                  * the batching benefits but not so much that we create dead time on the wire.
 790                  */
 791                 if (ic->i_unsignaled_wrs-- == 0) {
 792                         ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
 793                         send->s_wr.send_flags = IB_SEND_SIGNALED;
 794                 }
 795
 796                 send->s_wr.opcode = op->r_write ? IB_WR_RDMA_WRITE : IB_WR_RDMA_READ;
 797                 send->s_wr.wr.rdma.remote_addr = remote_addr;
 798                 send->s_wr.wr.rdma.rkey = op->r_key;
 799                 send->s_op = op;
 800
 801                 if (num_sge > rds_ibdev->max_sge) {
 802                         send->s_wr.num_sge = rds_ibdev->max_sge;
 803                         num_sge -= rds_ibdev->max_sge;
 804                 } else {
 805                         send->s_wr.num_sge = num_sge;
 806                 }
 807
 808                 send->s_wr.next = NULL;
 809
 810                 if (prev)
 811                         prev->s_wr.next = &send->s_wr;
 812
 813                 for (j = 0; j < send->s_wr.num_sge && scat != &op->r_sg[op->r_count]; j++) {
 814                         len = ib_sg_dma_len(ic->i_cm_id->device, scat);
 815                         send->s_sge[j].addr =
 816                                  ib_sg_dma_address(ic->i_cm_id->device, scat);
 817                         send->s_sge[j].length = len;
 818                         send->s_sge[j].lkey = ic->i_mr->lkey;
 819
 820                         sent += len;
 821                         rdsdebug("ic %p sent %d remote_addr %llu\n", ic, sent, remote_addr);
 822
 823                         remote_addr += len;
 824                         scat++;
 825                 }
 826
 827                 rdsdebug("send %p wr %p num_sge %u next %p\n", send,
 828                         &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
 829
 830                 prev = send;
 831                 if (++send == &ic->i_sends[ic->i_send_ring.w_nr])
 832                         send = ic->i_sends;
 833         }
 834
 835         /* if we finished the message then send completion owns it */
 836         if (scat == &op->r_sg[op->r_count])
 837                 prev->s_wr.send_flags = IB_SEND_SIGNALED;
 838
 839         if (i < work_alloc) {
 840                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
 841                 work_alloc = i;
 842         }
 843
 844         failed_wr = &first->s_wr;
 845         ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
 846         rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
 847                  first, &first->s_wr, ret, failed_wr);
 848         BUG_ON(failed_wr != &first->s_wr);
 849         if (ret) {
 850                 printk(KERN_WARNING "RDS/IB: rdma ib_post_send to %pI4 "
 851                        "returned %d\n", &conn->c_faddr, ret);
 852                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
 853                 goto out;
 854         }
 855
 856         if (unlikely(failed_wr != &first->s_wr)) {
 857                 printk(KERN_WARNING "RDS/IB: ib_post_send() rc=%d, but failed_wqe updated!\n", ret);
 858                 BUG_ON(failed_wr != &first->s_wr);
 859         }
 860
 861
 862 out:
 863         return ret;
 864 }
 865
 866 void rds_ib_xmit_complete(struct rds_connection *conn)
 867 {
 868         struct rds_ib_connection *ic = conn->c_transport_data;
 869
 870         /* We may have a pending ACK or window update we were unable
 871          * to send previously (due to flow control). Try again. */
 872         rds_ib_attempt_ack(ic);
 873 }